Hi, Chris!
Congratulations on your first cruise -- you have made a wise choice by booking a Disney Cruise Line (DCL) vacation!
Most guests finalize their shipboard account before Debarkation Day -- usually on the last afternoon or evening. You will receive a print out under your door on Debarkation Day, but there will no "hidden charges." You should be fully aware of when you're purchasing items or services on board -- you'll have to sign for them. There are government taxes and fees associated with every cruise. However, those are usually settled with your cruise booking before you ever set sail.
As far as gratuities, they will be added to your shipboard account only if you go to Guest Services and pay them before the last evening of your cruise. Otherwise, you can prepay them before you ever leave home, or you can put cash in the gratuity envelopes.
For more information and guidelines on gratuities (who and what to tip), there's a great chart on
DisneyCruise.com which will help you out, but let me know if you have more questions. Have a wonderful day and fabulous vacation.
Bon voyage,
Andi